Add addToGitIgnore to cli-kit to append entries to existing .gitignore files

[karreiro]

WHY are these changes introduced?

This PR moves the addToGitIgnore to cli-kit, following the suggestion in this thread #5184 (comment)

WHAT is this pull request doing?

This PR moves the addToGitIgnore from the theme package to cli-kit, following the suggestion in the thread above.

How to test your changes?

• Run shopify theme metafields pull
• Notice that, when the .shopify/metafields.json file is created, .shopify is also added in the gitignore

Post-release steps

N/A

Measuring impact

How do we know this change was effective? Please choose one:

• n/a - this doesn't need measurement, e.g. a linting rule or a bug-fix
• Existing analytics will cater for this addition
• PR includes analytics changes to measure impact

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟡	Statements	75.36% (+0.04% 🔼)	8902/11812
🟡	Branches	70.59% (+0.03% 🔼)	4328/6131
🟡	Functions	75.14% (+0.05% 🔼)	2340/3114
🟡	Lines	75.9% (+0.05% 🔼)	8413/11084

Show files with reduced coverage 🔻

St.❔	File	Statements	Branches	Functions	Lines
🟢	... / app-event-watcher.ts	93.83% (-1.23% 🔻)	86.49% (-2.7% 🔻)	90.48%	98.61%

Test suite run success

2005 tests passing in 905 suites.

Report generated by 🧪jest coverage report action from ab407f3

[frandiox]

Thank you!!

[github-actions]

Differences in type declarations

We detected differences in the type declarations generated by Typescript for this branch compared to the baseline ('main' branch). Please, review them to ensure they are backward-compatible. Here are some important things to keep in mind:

• Some seemingly private modules might be re-exported through public modules.
• If the branch is behind main you might see odd diffs, rebase main into this branch.

New type declarations

We found no new type declarations in this PR

Existing type declarations

packages/cli-kit/dist/public/node/git.d.ts

@@ -27,6 +27,16 @@ export interface GitIgnoreTemplate {
  * @param template - The template to use to create the .gitignore file.
  */
 export declare function createGitIgnore(directory: string, template: GitIgnoreTemplate): void;
+/**
+ * Add an entry to an existing .gitignore file.
+ *
+ * If the .gitignore file doesn't exist, or if the entry is already present,
+ * no changes will be made.
+ *
+ * @param root - The directory containing the .gitignore file.
+ * @param entry - The entry to add to the .gitignore file.
+ */
+export declare function addToGitIgnore(root: string, entry: string): void;
 /**
  * Options to use when cloning a git repository.
  *